1. Field of the Invention
The present invention relates to a lithium ion secondary battery.
2. Description of Related Art
Japanese Patent Application Publication No. 2011-210694 (JP 2011-210694 A) discloses a technique in which an inorganic ferroelectric having a dielectric constant of 500 or higher is sintered on a surface of a positive electrode active material.
An electrolytic solution for a lithium ion secondary battery is an ion conductor in which a lithium (Li) salt is dissolved in a nonaqueous solvent. In the electrolytic solution, the Li salt is ionized into Li ions (cations) and counter anions. However, actually, ion association which is a reverse reaction to ionization occurs, and thus complete ionization does not occur. In the electrolytic solution, the number of ionized free ions is large, and as the movement of free ions becomes faster, the electrical conductivity increases.
According to JP 2011-210694 A, the inorganic ferroelectric is sintered on the surface of the positive electrode active material. As a result, in an interface between the positive electrode active material and the electrolytic solution, the ionization of the Li salt is promoted, and output characteristics of a battery are improved. However, output characteristics are not insufficient for an application such as a vehicle-mounted battery where extremely high output characteristics are required.